1. Field of the Invention
The present invention relates to a washing machine, and more particularly, to a washing machine provided with a dual-purpose sensor for detecting a degree of vibration generated during a dewatering step and for measuring detergent levels present in the water.
2. Discussion of the Related Art
Generally speaking, a washing machine is an apparatus for removing dirt from laundry through such steps as washing, rinsing, and dewatering in accordance with a program stored in a microcomputer. Typically, a variety of operational features are provided using a plurality of sensors and detectors for inputting status signals to the microcomputer, so that the washing machine may be controlled as desired.
Referring to FIGS. 1 and 2, a washing machine according to a related art is comprised of a body 1 having a door 2 on a top of the body; an outer tub 5, installed inside the body, for holding water; an inner tub (dewatering tub) 6, installed inside the outer tub, having a multitude of perforations formed in a circumferential surface thereof to perform a dewatering step through a centrifugal force generated by the drive unit rotating the inner tub at high speed; a pulsator 7, installed in the bottom of the inner tub, receiving the drive force of a drive unit consisting of a motor 3 and a clutch 4, to agitate the water during a washing step; a drain pump 8 for draining the water; a microcomputer 10 for controlling the overall system; and a sensor 9 provided with a pair of electrodes 9a and 9b installed with respect to the outer tub for detecting the level of a detergent present in water within the outer tub. The first electrode 9a is connected to a supply voltage (Vcc), which is connected to an input port of the microcomputer 10 via a pull-up resistor, and the second electrode 9b is connected to ground. Though not specifically shown, the installation of the first and second electrodes 9a and 9b, which are separated by a predetermined distance, is such that both electrodes are submerged in water filling the outer tub 5.
In performing a washing step using the above-constructed washing machine, laundry is placed in the inner tub 6, which has an open top through which the laundry is passed via the door 2 of the body 1 and an open top of the outer tub 5. Then, water is supplied to the outer tub 5 through a water supply valve (not shown) after placing laundry in the inner tub 6. The outer tub is filled to a predetermined level, and detergent is added to the water. The pulsator 7 agitates the water, generating a roiling current to cause friction with the laundry and perform a washing step. Upon completion of the washing step, the drain pump 8 is actuated to drain the majority of the water, after which the inner tub 6 is rotated at high speed, thus using centrifugal force to remove the laundry's remaining water content.
In the washing step, once the water flows in the inner tub 6, the first and second electrodes 9a and 9b are electrically connected to each other so that the input port of the microcomputer 10 is grounded through the water and detergent, which is a contaminant. The detergent content of the water creates a resistance according to known rates, so that the microcomputer 10 can measure the amount of detergent present in the water. Namely, as the amount of the detergent increases, the resistance between the first and second electrodes 9a and 9b increases. The thus varying voltage applied to the input port of the microcomputer 10 is detected to measure the detergent level.
In providing a washing machine with a variety of operational features, it is desirable to impart the washing machine's sensors and detectors with maximum versatility. In the above washing machine according to the related art, however, the sensor 9 is an electrode-type sensor that measures the level of detergent content in the water, using a detected voltage across the first and second electrodes 9a and 9b, but is unable to play the role of another sensor.